This invention relates to a three-color copying machine capable of reading three colors of an original and recording them, and more particularly to a three-color copying machine which uses two image sensors to read three different colors.
When the same optical image is formed on two image sensors and the images are different from one another in wavelength, processing the resultant image signals provides image signals of two colors.
FIG. 1 shows a reading section of a conventional copying machine for recording data in two colors, namely, black and red. An original 3 is subjected to slit exposure by a pair of fluorescent lamps 1 and 2, and is subjected to auxiliary scanning in the direction of the arrow. A light beam reflected from the original 3 passes through a lens 4 and is then split into two light beams proceeding in two directions by a half-mirror 5, as a result of which the same optical image is formed on first and second image sensors 6 and 7. The first image sensor 6 subjects the optical image to photo-electric conversion irrespective of wavelength, to provide an image signal 8 for each line. On the other hand, the second image sensor 7 subjects the optical image, the red wavelength components of which have been absorbed by a cyan filter 9 disposed thereabove, to photo-electric conversion, to provide an image signal 11 for each line. These image signals 8 and 11 are supplied to a color separating circuit 12, where they are subjected to binary-encoding and logical operations. As a result, a red image signal 13 representing red data and a black image signal 14 representing black data are obtained.
With the above-described copying machine, colors other than the two given recording colors of course cannot be recorded as they are; that is, such colors are not recorded at all or are recorded in one of the two recording colors. Accordingly, the resultant copy gives an impression which it is considerably different from the original.